In digital video, an alpha channel is used to define the transparency of the video when that video is mixed with a background image or background video. For example, a source video may undergo a transformation in video production equipment to produce an effect (e.g. the shrinking and/or rotating of the source video), and then the resultant transformed source video may be layered on top of a background image or background video. The alpha channel defines the transparency of the transformed source video when it is layered on top of the background image or background video. For example, an alpha channel can be used to make the transformed source video semi-transparent.
A shaping alpha is an alpha channel that defines the boundaries of the transformed source video when the transformed source video is layered on top of a background image or video. In particular, it has been found to be aesthetically pleasing to a human eye to have the transformed source video fade into the background image or background video at the boundaries of the transformed source video. This may be achieved through the use of a shaping alpha that defines the semi-transparency of the transformed source video at or around its boundaries.
Methods and systems for computing the shaping alpha in video production equipment are desired.